Dielectric Functions and Interband Critical Points of Anisotropic Chain Structured Tlse Single Crystals

Abstract

Spectroscopic ellipsometry measurements were carried out on TlSe single crystals for orientations of electric field, parallel (E parallel to c), and perpendicular (E perpendicular to c) to optic axis c. The experiments were performed in the 1.2-6.2 eV spectral range at room temperature. The real and imaginary parts of the pseudodielectric function as well as pseudorefractive index and pseudoextinction coefficient were calculated from the analysis of ellipsometric data under the light of ambient-substrate optical model. The energies of interband transitions (critical points) have been found from the analysis on second derivative spectra of the pseudodielectric function. The analysis revealed four and five interband transition structures for E parallel to c and E perpendicular to c configurations, respectively. The obtained critical point energies were assigned tentatively to interband transitions using the available electronic energy band structure given in literature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4761963]